Solutions | GESAC Harmonic Reducer Flexible Gear Solution: Overcoming the Challenges of Machining Gear Components for Robots
Solutions | GESAC Harmonic Reducer Flexible Gear
Due to their compact size, high precision, minimal backlash, and smooth operation, harmonic reducers are widely used in precision joint drive modules for industrial robots, as well as in light-load, high-precision joints such as the arms, wrists, and necks of humanoid robots. As core drive components, they enable lightweight, flexible robots to perform precise and delicate movements and achieve high repeatability in positioning.
A harmonic reducer primarily consists of precision components such as a rigid gear, a flexible gear, and a wave generator. Its operating principle is as follows: the wave generator induces controllable elastic deformation waves in the flexible gear; these deformation waves then interact with the rigid gear, thereby enabling motion and power transmission. Only when it operates extremely smoothly can it meet the requirements for precise adjustment of robotic joint rotation.
As a key component, the flexible gear is a thin-walled elastomeric part with an external gear ring. It generally comes in two forms: cup-shaped and cap-shaped. Both types feature an external gear at the open end. The gear module typically ranges from m0.1 to m1.5. Common materials include alloy steels such as 40CrNiMoA and 40CrA, with a quenched and tempered hardness of approximately HRC 30–35, and after heat treatment, the hardness can reach approximately HRC 55–60.
Key Challenges
- Precision turning of the bore as a reference for gear hobbing: if the cutting tool cannot perform precise and stable cutting, it is difficult to control the machining allowance. If the allowance is too small, heat treatment distortion cannot be eliminated; if the allowance is too large, honing efficiency is low and the bore is prone to losing its roundness.
- Machining thin‑walled parts with a small‑module hobbing cutter: if the cutting forces on the cutter edges are uneven, stress release can easily cause deformation, and the cutter edges are prone to chipping and chip buildup, which can lead to defects such as concavity in the tooth profile and chatter marks.
GESAC introduced a comprehensive machining solution for harmonic reducer flexible gears. For external cylindrical and end‑face turning, the company primarily recommends new negative‑type P‑series inserts and recommends new positive‑type U‑series inserts for internal cylindrical turning, the D938 series twist drills for hole machining. The most critical external gear cutting operations are performed using GESAC new flexible‑wheel gear hobbing cutters.
Application Cases
GESAC new GPT6220 steel insert is designed for fine to semi‑fine machining of carbon steel and alloy steel under high‑speed, continuous operating conditions. Featuring a negative PF flute profile, it enables long‑life cutting of external circular surfaces with flexible wheels. Under identical operating conditions, the tool life of our products is 50% longer than that of foreign tool brands.
GESAC new steel cutting tool, model GPT6220, features a standard UL flute design, enabling low‑resistance cutting of the inner circle of flexible wheels. Under identical operating conditions, the tool life of our products is 66% longer than that of foreign tool brands.
The customer requires the surface roughness of the inner circle to be controlled within Ra 0.8. By using our Hummingbird Series VCGT11T302M‑BK‑GAT7115 inserts, we can achieve high surface quality during finishing. Under the same operating conditions, the tool life of our products is 20% longer than that of foreign tool brands.
For machining end‑face holes in flexible wheels, using our D938 series general‑purpose steel twist drills ensures excellent hole positioning accuracy. Under identical machining conditions, the tool life of our products is 15% longer than that of foreign tool brands.
The core process in flexible‑wheel machining is the hobbing of external gear rings. By using GESAC new generation of flexible‑wheel‑specific hobbing tools, high‑precision forming of gears with a module of less than m0.2 can be achieved, with machining accuracy reaching AAA grade. The specific machining plan is as follows.
Harmonic reducers are the “heart” of robotic joints, and the machining of flexible gears is a challenging hurdle in the manufacturing process. GESAC has deepened its expertise in the field of precision cutting. Through comprehensive tooling combinations and practical process solutions, we have systematically addressed mass production pain points such as thin‑walled part deformation, tooth profile defects, and excessive tool wear, demonstrating the proven reliability of domestically produced cutting tools with concrete data. Riding the wave of domestic substitution, we will continue to ramp up R&D in precision machining technology for robots. Through one‑stop solutions, we will support more transmission companies in overcoming manufacturing bottlenecks, jointly propelling China’s industrial and humanoid robotics industries toward a new phase of higher precision and larger scale.
Author: GESAC